Television receiving apparatus



'Aug4, 1936.-

G. SCHUBERT 'TELEVISION -REcEggv1NG APPARATUS Filed April 20, 1932Patented ug. 4, 11.936

UNITED STATES I TELEVISION RECEIVING Georg Schubert, Berlin, Germany,assigner to the firm Fcrnsh Aktien-Gesellschaft, Zehlendorf,

near Berlin, Germany Application April 20, 1932, Serial No. 606,471 InGermany April 24, 1931 4 claims. (ol. 17a-s) In television practice thesources of light usually employed for giving a luminous'surface are theknown surface glow'discharge lamps. The

ordinary surface glow discharge lamp has the 5 advantage that it can becontrolled with simple means and without particular expenditure, but inthe case of high image point numbers it provides relatively fainttelevision pictures.

'1t hasm fact already been proposed to en.

l0. ploy the positive column of gas discharges, but heretofore, in ordertobe freefrom disturbances, they have been operated with modulated highfrequency,` exceedingly high voltages being required for this purpose.Moreover it has not been possible to eliminate these disadvantages evenby employing oxide cathodes. Heretofore, for the. operation of luminoustubes it has always been necessary to employ a high-frequencytransmitting valve with low frequency modula- In contradistinction tothe previous compli cated methods of operating with high frequency, thepresent invention consists in operating the luminous tube withcontinuous voltage and in connecting it.directly in series with theoutput valve of the low-frequency amplifier, so that the anode .currentofthe output valve, for example an R E 604, vflows through the luminoustube. In contradistinction to any other method of I0 coupling, auch aschokes, transformers, etc., this circuit connection has the additionaladvantage of working perfectly independently of the frequency. It isimmaterial whether the luminous tube is provided with a. heatedcathodeor not,

85 and likewise, the cathode may be heated by 'direct current oralternating current.

Certain difficulties arise, however, in operating the positive-columnluminous tube with continuous voltage. The luminous tube is'readily 40extinguished at the moment modulation begins, and with modulation ofvarying strength it works so irregularlyy as to be unsuitableforsatisfactory reproduction. As mentioned hereinbefore this unreliableworking has also'rcsulted 45 in the fact that heretofore luminous tubes-were never operated with continuous voltage but always withhigh-frequency, because the dimculties do not then occur. According to afeature of the present inven- 50 tion, all the aforementioneddifficulties in the operation of luminous tubes with continuous voltagemay .be obviated by exciting the luminous tube with high frequency. Verysmall outputs are sufficient for this, and quite ordinary broadcastingvalves, for example an R. E 134 or weaker valves, will suiiice'.l Thecoupling of the Y high frequency is preferably effected capacitativelyand, since very small'capacities are suilicient for coupling, this maybe done by simply placing behind the luminous tubes a metal plate o towhich is connected a lead from the highfrequency circuit. The other leadis preferably connected directly to the cathode. At the same time, themetal plate used for capacity coupling may also be constructed in theform of a me- 1o tallic mirror, in which case it will increase theuniformity of the luminosity of the image surface.

The accompanying drawing shows the complete circuit of a luminous tubefortelevision 16 purposes,the said tube being, according to theinvention, operated with continuous voltage and excited with highfrequency. In the drawing, the output valve of the low frequencyamplifier 'is shown at I, 2 is the luminous tube connected 20 in seriestherewith, 3 is the oscillating valve for generating the high frequencyand 4 is the metal plate or metallic mirror which is used for thecapacity coupling of the luminous tube to the high-frequency circuit. Aresistance 5 bridged 25 by a capacity 6 is used for regulating thecurrent intensity of the luminous tube. All the remaining details willbe gathered without diillculty from the circuit diagram itself.

' Having now particularly described and ascer- 30 tained the nature ofmy said invention and in whatV manner the same is to be performed, Ideclare that what I claim is:-

l. In a television system, the combination of a low-frequency amplifierhaving an outputvvalve, a variable resistance and a positive-columnluminous tube having a` descending current voltage characteristics andhaving its electrodes spaced longitudinally of the tube connected inseries with said resistance in the anode circuit `of said output valve,a condenser is shunt to said resistance, and means for continuouslycapacitatively exciting said luminous tube with high frequency.

2. The combination in a television system, of a low frequency amplifierhaving an output valve, a positive-column luminous tube and means forcontinuously capacitatively exciting said luminous tube with highfrequency, means for connecting said positive-column luminous tube iqthe anodecircuit of said output tube including a variable resistancearranged in a lead connecting one electrode of said luminous tube withthe anode of said output tube, and a condenser shuntedacrossgsaidiesistan :e., v 55 3. The combination in a television system, of a lowfrequency amplifier having an output valve, a positive-column luminoustube and meansy for continuously capacitatively exciting said luminoustube with high frequency, means for connecting said positive-columnluminous tube in the anode circuit of said output tube including avariable resistance arranged in a lead connecting one electrode of. saidluminous tube with the anode of said output tube, and a condenser inshunt to said resistance, said means for capacitatively exciting saidluminous tube with high frequency including .a high frequency circuit,an oscillating valve for generating high frequency in said highfrequency circuit, and a metallic plate connected with said last namedcircuit and arranged behind said luminous tube for establishing acapacitative coupling between said high frequency circuit and saidluminous tube. i

4. The combination in a television system, of

a low frequency amplifier having an output valve, a positive-columnluminous tube and means for continuously capacitatively exciting saidluminous tube with high frequency, means for connecting saidpositive-column luminous tube in the anode circuit of said output tubeincluding a variable resistance arranged in a lead connecting oneelectrode of said luminous tube with the anode of said output tube, anda condenser in shunt to said resistance, said means for continuouslycapacitatively exciting said luminous tube with high frequencycomprising an independent high frequency circuit, an oscillating valvefor generating high frequency in said highy frequency circuit, and ametallic plate having a reflecting surface connected with said lastnamed circuit and arranged behind said luminous tube for establishing acapacitative coupling between said high frequency circuit and saidluminous tube.

GEORG SCHUBERT.

